Oscillation-control circuits



F. H. DALET OSCILLATION CONTROL CIRCUITS Original Filed Feb. 21, 1925 I A7 Q 2 1111 111 WW- I Fun/EHDQM +3 INVENTOR I ATYORN EY Patented Aug. 14, 1928.

rnnuxn. DALET, or NEW YORK, N. Y.

ATE T OFFICE.

OSCILLATION-CONTROL crncun's.

Application filed lebruaiy 21, L825, Serial No. 915 B enewed April 27, 192 8.

- "This invention relates to circuits used in t the transmission and reception ofradio conmiunications or in wireless telegraphy and. telephony, and has for its object the provision of means interposed inland forum ing a part of a xtransmittingnor receiving circuit whereby to control oscillations and prevent undesired noises.

It is well known that in a receiving apparatus when an outputcircuit is transferring its energy or power to the input circuit of an amplifier free oscillations are set up which produce a loud squealing or whistling noise seriously interfering with reception and resulting in distortion and sometimes even obliteration of the desired sig nals. It is also known that the advantages attendant upon suchtransfer of power cannot ordinarily be avoided, owing to the internal capacity of the thermionic triodes or vacuum tubes used as amplifiers.

It is with the above facts in view that I have designed the present invention which is calculated to eliminate the objectionable features by'a system of absorption, the disturbance producing energy being (carried off to the ground instead of being permitted to pass to the successive amplifiers.

An important and more specificobjectis the provision of a circuit including inductances in series with theafilament heating current for the tubes. and electro-magnetically coupledto the first inductance and to the transformer couplings between the successive tubes. a t 1 A furtherobject is the provision of control means of this character/in which the energy absorbing andlcarrying ofl' inductances may be adjusted with respecttto the adjacent and .associated transformers in order to vary the coupling and control the free oscillations so that the desired signals may be received clearly and unmixed with noises resulting from disturbances in the circuit.

With the above objects andadvantages in view, the invention may consist in the arrangement of inductances connected in the circuit as will be hereinafter more fully described and claimed and illustrated in the accompanying drawing in which: 7

Figure 1 is a. diagram of the preferred circuit arrangement,

Figure 2 is a diagram of a modification,

a primary coil 4 connected with the aerial 5 and ground 6, this primary being located in magnetically coupled relation to a sec: ondary coil 7 which may beisplit, as indicated in Figure 1 or not, as indicated in Figure 2, this detail being capable of variation within the scope of the invention. One

terminal of the secondary is shown as leading to the grid of the first amplifying tube 8 while the other terminal is represented as connected with one of the leads from the filament battery 9 to the filament 10. The first tube 3 is represented as coupled to the next tube 2 by means of a similar inductance including a primary coil ll interposed be-' tween the plate 12 of the first tube and the positive terminal of the high potential or B battery 13. This primary coil 11 is coupledto a secondary coil 1 1 having one terminal connected with the grid 15 of the second tube and its otherterininal connected with one of the leads to the filament 16 thereof. The second amplifying tube is coupled to the detector tube 1 by a similar inductance including coils 17 and 18 arranged in the same manner, thelatter being connected to the grid 190f .thedetector tube 20 and with the lead to the filament 21 thereof. In each instance the secondary coil is shown as shunted by a variable capacity 22 as is customary.

In carrying out the present invention I provide an auxiliary or compensating inductance coupled to each; of the above- 111 811- tioned inductances. These compensating inductances are represented as coils 23, 24 and 25 located adjacent the respective inductances which transfer theenergyto thesuc cessive tubes and itisobvious that thespecific construction, arrangement and mounting of these auxiliary coils may be varied within wide limits as I do not wish to be limited in this respect. However, it is in tended that the auxiliary coils be, in some manner, movably mounted or otherwise arranged and related to the respective induc- I ll tances in order that the coupling may be varied. These coils may be considered to a certain extent as tickler" coils inasmuch as they carry a portion of the radio frequency current.

The compensating coils are shown as having one terminal connected with the negative side of the A-balitery whereas other ter1ni nals are connected with the filaments of the respective triodes or vacuum tubes in such manner that all of these coils will be arranged in series with the filament and filament control rheostats of the vacuum tubes in the respective stages. It is preferable, however, that the terminals of the coil 23 be reversed with respect to those of the coils 2i and 25 inasmuch as better results are thus obtained. It is, however, conceivable that the connections might be the samein each instance. Entirely regardless of the reversal of the connections it should be repeated that in each stage the oscillation control coil 23, Qet or 25, as the case may be, is in series between the filament, the filament control rheostat and the filament battery of each tube or triode.

The arrangement of the coil 23 with respect to the adjacent inductance is such that they have the same polarity whereby the external electro-motive force impressed upon the coil 23 will act upon the field surrounding the inductance to boost up or amplify the current passing therethrough, consequently increasing the energy and building up the signal strength. The coils 24 and 25 are both preferably arranged to have the same polarity as each other but they are oppositely wound or else have their terminals reversed with respect to the coil 23 in order that their fields will oppose the fields of the adjacent inductances and consequently absorb the free oscillations set up therein by the action of the vacuum tubes and conduct the undesired energy to the ground. In this way it is evident that the energy of these oscillations will be prevented from passing to the detector tube 20 and objectionable noises and disturbances which would otherwise interfere with the signals are eliminated.

In the operation it will be seen that adjustment of the auxiliary or compensating coil may be made independently for each vacuum tube or amplifying unit so that the maximum beneficial results will be insured.

From the foregoing description and a study of the drawing it will be apparent that I have thus provided a very simple and easily arranged auxiliary inductance coupled to the usual energy transferring induetances whereby to prevent the transference and building up of free oscillations so that the sensitiveness of the receiving apparatus will be increased while at the same time freedom from whistling, squealing and other audible results of the transference of electrical disturbances will be eliminated.

While a specific connection is disclosed, it should be understood that the induction coils may be positioned at different points within the filament or grid circuits whereby the same effect may be obtained, there being no limitation in this respect.

While I have shown and described preferred forms of the invention, it should be understood that the disclosure is merely illustrative inasmuch as I reserve the right to make all such changes in the detailed ar- -angement, location and combination of the elements as will widen the field of utility and increase the adaptability of the invention provided such changes contitute no dcparture from the salient features of the in vention or the scope of the appended claims.

Having thus described the invention, I claim:

1. In a radio receiving circuit embodying a plurality of stages each including a thermionic triode, inductances coupling the plate and grid circuits of the successive stages, and oscillation preventing means embodyin r coils arranged in inductive relation to sai inductances and connected in series with the filament battery, the rhcostats and the respective filaments of the triodes whereby to utilize the resistance thereof.

2. In a radio receiving circuit embodying a detector stage and successive stages of amplification, each stage embodying a thermionic triode including filament, grid and plate elements, inductances arranged to couple the plate and grid circuits of the successive stages, and oscillation control means comprising other inductances arranged in variable inductive relation to the first named inductances with certain of the last named inductances arranged in inverse relation, said second named inductances being connected in series with the filament current supply, the filaments and control rheostats therefor whereby to utilize the resistance thereof.

In testimony whereof I allix my signature.

FRANK H. DALET. 

